526 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



over tlio milled Leads, nnd if tlic hand is inadvortoiitly applied to 

 it, it revolves freely without acting on the milled head, and the 

 object is tluis saved from destrnction. 



Messrs. Powell and Lealand arc tlic designers of two earlier 

 forms which have been in use some years (figs. 118 and 110). The 

 former is identical in prineiidc with that just described, the only dif- 

 ference being that the cut ring is broad and substantial, wliich obviates 

 the liability to " spring," unavoidable in the case of a thin ring. 



Fig. 118. 



Fir., lilt. 



Their still older form (fig. 119) has the deep ring only, which has 

 two pins and a screw projecting inwards. When the latter is with- 

 drawn the ring can be slipped over the milled heads, and when 

 screwed home the ring is prevented fx'om slipping off, but revolves 

 freely, as in the other forms. 



Fabre-Domergue's Current Apparatus.* — M. P. Fabrc-Domer- 

 guc suggests the following apparatus, as not possessing the incon- 

 venience of monopolizing the Microscope and rendering " all other 

 observation impossible if only one instrument is at our disposition." 



A metal plate 4 cm. by 15 cm., with a central aperture, is placed on 

 the stage. One end projects 4 cm. beyond the stage, and sui^ports a 

 small cup of water at the level of the stage. The other end is bent 

 twice at a right angle, and the horizontal portion supports a second 

 cup, about 1 cm. below the stage. Two threads keep up the com- 

 munication between the cup and the object in the centre. When not 

 under observation the plate can be removed from the stage, and 

 rejdaced without disturbing the preparation or interrupting the 

 current of water. 



Moist Chamber. — A simple moist chamber can be made by cut- 

 ting a piece of thick rough cardboard to the size of the slide, and 

 punching out a circular hole in the centre of such a size as to be 

 covered by a cover-glass. The piece of cardboard is then soaked in 

 water (or boiled in water when pure cidtures of fungi are to be made) 

 so as to saturate it, and placed on the slide. The object is immersed 

 in a drop on a cover-glass, and the latter inverted over the hole in the 



* Bull. Soc. d'llist. Nat. Toulouse, xviii. (1884) pp. 1C2-3. 



